Abstract
High‐resolution measurements from Global Navigation Satellite System (GNSS) radio occultation (RO) provide atmospheric profiles with independent information on altitude and pressure. This unique property is of crucial advantage when analyzing atmospheric characteristics that require joint knowledge of altitude and pressure or other thermodynamic atmospheric variables. Here we introduce and demonstrate the utility of this independent information from RO and discuss the computation, uncertainty, and use of RO atmospheric profiles on isohypsic coordinates—mean sea level altitude and geopotential height—as well as on thermodynamic coordinates (pressure and potential temperature). Using geopotential height as vertical grid, we give information on errors of RO‐derived temperature, pressure, and potential temperature profiles and provide an empirical error model which accounts for seasonal and latitudinal variations. The observational uncertainty of individual temperature/pressure/potential temperature profiles is about 0.7 K/0.15%/1.4 K in the tropopause region. It gradually increases into the stratosphere and decreases toward the lower troposphere. This decrease is due to the increasing influence of background information. The total climatological error of mean atmospheric fields is, in general, dominated by the systematic error component. We use sampling error‐corrected climatological fields to demonstrate the power of having different and accurate vertical coordinates available. As examples we analyze characteristics of the location of the tropopause for geopotential height, pressure, and potential temperature coordinates as well as seasonal variations of the midlatitude jet stream core. This highlights the broad applicability of RO and the utility of its versatile vertical geolocation for investigating the vertical structure of the troposphere and stratosphere.
Highlights
Precise knowledge and understanding of the thermodynamic state of the atmosphere and the global atmospheric circulation is crucial when investigating the physical climate system, climate variability and change [e.g., Intergovernmental Panel on Climate Change, 2013]
High-resolution observations from radio occultation (RO) measurements provide virtually independent information on altitude and pressure. This unique property among satellite-based observational systems is important because it ensures equivalent data quality on isohypsic (MSL altitude and geopotential height) and thermodynamic vertical coordinates
Their uncertainty is only limited by the choice of the Earth geoid model and its horizontal resolution as well as the accuracy of the Earth gravity model
Summary
Precise knowledge and understanding of the thermodynamic state of the atmosphere and the global atmospheric circulation is crucial when investigating the physical climate system, climate variability and change [e.g., Intergovernmental Panel on Climate Change, 2013]. In this context, the upper troposphere and lower stratosphere (UTLS) region is important because of different characteristics of the well-mixed troposphere and the stably stratified stratosphere as well as their vertical coupling and interaction [e.g., Gerber et al, 2012]. Changes of the atmospheric circulation system have become evident as, for example, the expansion of the tropical belt [e.g., Seidel et al, 2008; Davis and Rosenlof , 2012]. Since these changes in global atmospheric circulation are small, accurate, precise, and global data are required to get reliable information
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